1. Field of the Invention
The present invention relates to a nonwoven elastomeric material which may be used to impart elastic properties to flexible, non-elastic substrates.
2. Description of the Related Art
Vulcanized rubber or synthetic rubber elastic bands or threads have typically been used to provide elastic properties to flexible substrates by attaching the elastic to the substrate using materials such as thread, yarn, or adhesive in a sewing, weaving, or adhesive process.
For some time, those in the art have been attempting to form elastomeric resins into nonwoven elastomeric materials. For example, attempts have been made to form nonwoven elastomeric webs utilizing elastomeric resins, such as various polystyrene/poly(ethylenebutylene)/polystyrene elastomeric block copolymers. One problem associated with such elastomeric resins, however, is that such elastomeric resins are generally too viscous to be extruded alone without substantial melt fracture of the product.
Thus, many such elastomeric resins need to be blended with a fatty chemical, such as stearic acid, prior to extrusion so as to overcome the viscosity problem. However, physical properties of the product obtained by this process, for example, a nonwoven mat of meltblown fibers, are typically unsatisfactory. After formation of the nonwoven web, substantially all the fatty chemical may be leached out of the nonwoven web of extruded microfibers by soaking the web in alcohols having a good ability to solubilize the fatty chemical utilized.
In order to overcome the above-stated viscosity problems, it is known to form elastomeric block copolymer materials into nonwoven elastomeric products by providing extrudable compositions which are blends of a block copolymer and a processing aid, such as a polyolefin. When blended with the block copolymer and subjected to appropriate elevated pressure and elevated temperature conditions, the processing aid is extrudable in blended form with the block copolymer. The presence of the processing aid in the blend generally serves to reduce the viscosity of the composition as compared to the viscosity of the pure block copolymer and, thus, enhances the extrudability of the composition. However, the use of such processing aids typically negatively affects the elastic properties of the prepared nonwoven elastomeric product as compared to the elastic properties of a nonwoven elastomeric product prepared from a pure block copolymer.
Thus, a void exists with respect to extrudable compositions for forming nonwoven elastomeric materials that can be easily manufactured and that have desirable elastic properties. Furthermore, a void exists with respect to such nonwoven elastomeric materials which can be used to impart elastomeric properties to a composite laminate.